An optical scanning projection system includes a scanning light source component, a second reflecting element, a transparent element, a scanning element, a photosensitive element and a control module. The transparent element receives a main light beam emitted by the scanning light source component and reflects a part of the main light beam to be a reflected light. The reflected light is reflected by the second reflecting element, and the scanning element reflects the reflected light from the second reflecting element in a scanning manner. The photosensitive element receives the reflected light from the scanning element and outputs a sensing signal, and the control module actuates or stops actuating the scanning light source component according to the sensing signal. Therefore, when the scanning element is damaged, the control module may instantly stop actuating the scanning light source component, thereby enhancing the using safety of the optical scanning projection system.